Boulder Creek, California Weather Forecast Discussion

090
FXUS66 KMTR 080429
AFDMTR
Area Forecast Discussion
National Weather Service San Francisco CA
929 PM PDT Sun Sep 7 2025
...New AVIATION, MARINE...
.KEY MESSAGES...
Updated at 259 PM PDT Sun Sep 7 2025
- Below normal temperatures through the week.
- Chance for light rain Monday through Wednesday.
&&
.UPDATE...
Issued at 851 PM PDT Sun Sep 7 2025
A good resurgence of coastal status tonight, with winds beginning
to weaken and mostly mild and around average temperatures
expected. Cloud cover continues to build through the night as the
next cold front approaches. Light rain chances arrive into Monday
as some pre-frontal light rain and drizzle in the North Bay. These
chances spread farther south amd east through the evening, with
high resolution models showing the main rain band along the front
arriving into the night. The overnight forecast package will have
a focus on the timing of the rain chances, but rainfall amounts
still look to be light across most models.
&&
.SHORT TERM...
Issued at 259 PM PDT Sun Sep 7 2025
(This evening through Monday night)
High clouds are flitting in from the upper level low pressure system
that will eventually bring rain chances to the Bay Area, and perhaps
parts of the Central Coast. Until that arrives, the main story for
tonight will be the return of the stratus. The marine layer is
poised to deepen to about 2500ft or so, which should allow for an
earlier onset of stratus for coastal locations. It will then seep
inland, leaving a good portion of the interior blanketed in stratus
by early morning. Coastal drizzle will be possible as well.
Eventually, stratus should clear for interior locations by late mid
to late morning. The aforementioned upper level low will creep
towards West Coast, which will bring an additional influx of high
clouds to the region.
The question then becomes, when will it rain? Latest NBM guidance is
a bit aggressive with the front and has chances arriving mid to late
morning. The more likely period will should be Monday afternoon and
evening for North Bay counties. Elsewhere chances increase late into
the evening, spreading as far south as northern Monterey and San
Benito counties. Confidence for measurable rain remains in highest
for the North Bay, where they could see up to 0.15" of rain. The
farther south you move into the Bay Area, chance decrease to maybe
0.05" or less whereas the Central Coast outside of the Santa Lucia
may see a few hundredths if the front makes it that far.
&&
.LONG TERM...
Issued at 259 PM PDT Sun Sep 7 2025
(Tuesday morning through next Saturday)
Upper level troughing dominates much of the period, leaving us with
unseasonably cool and potentially unsettled weather. Similar
thinking to the midshift and that we could see post frontal
convection Tuesday afternoon and evening, as the cold upper level
low moves inland. Cold air aloft, -15C at 500mb heights, daytime
heating with a couple hundred J/kg of CAPE, mediocre lapse rates of
6.5-7C, and some shear we should at least see some cumulus clouds
form. Showers are not out of the question given PWATS should we get
enough lift. A few rumbles of thunder are possible as well,
currently favoring the far northeastern Sonoma and northern Napa
counties.
The slow slowly meanders eastwards, Wednesday into Thursday with
showers retreating to the the terrain and perhaps North Bay
counties on Thursday. Weak upper level ridging should build in for
Friday, leaving us with drier and a hair warmer.
&&
.AVIATION...
(06Z TAFS)
Issued at 926 PM PDT Sun Sep 7 2025
Currently a mixed bag of IFR-VFR at the terminals. High
confidence in sub-VFR ceilings returning to all terminals tonight
with LIFR/IFR for coastal terminals and MVFR for bayshore and
interior terminals. Widespread VFR is expected by tomorrow
afternoon. An approaching low pressure system will have high
clouds lower through the TAF period with rain showers approaching
the California Coast towards the end of the 24 hour TAF period.
Vicinity of SFO...Currently VFR with westerly flow. High confidence
in an MVFR ceiling returning to the terminal tonight. Westerly winds
will prevail through the TAF period. Light rain showers will
approach the terminal towards the end of the TAF period.
SFO Bridge Approach...Similar to SFO.
Monterey Bay Terminals...Currently IFR and calm at MRY and MVFR with
northerly flow at SNS. High confidence in SNS further deteriorating
to IFR. Brief VFR will prevail by tomorrow afternoon. Westerly winds
will prevail through the TAF period.
&&
.MARINE...
(Tonight through next Saturday)
Issued at 926 PM PDT Sun Sep 7 2025
Moderate northwesterly breezes will prevail through Monday. Winds
increase to become fresh with strong gusts Tuesday through
Thursday. Light rain is expected tomorrow night into Tuesday
morning with slight chances for thunderstorms during the
afternoons of Tuesday through Thursday, chances increase with
latitude.
&&
.MTR WATCHES/WARNINGS/ADVISORIES...
CA...None.
PZ...None.
&&
$$
SHORT TERM...KR
LONG TERM....KR
AVIATION...Sarment
MARINE...Sarment
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NWS MTR Office Area Forecast Discussion